PHP calculate age

I’m looking for a way to calculate the age of a person, given their DOB in the format dd/mm/yyyy.

I was using the following function which worked fine for several months until some kind of glitch caused the while loop to never end and grind the entire site to a halt. Since there are almost 100,000 DOBs going through this function several times a day, it’s hard to pin down what was causing this.

Does anyone have a more reliable way of calculating the age?

//replace / with - so strtotime works
$dob = strtotime(str_replace("/","-",$birthdayDate));       
$tdate = time();

$age = 0;
while( $tdate > $dob = strtotime('+1 year', $dob))
{
    ++$age;
}
return $age;

EDIT: this function seems to work OK some of the time, but returns “40” for a DOB of 14/09/1986

return floor((time() - strtotime($birthdayDate))/31556926);

Answer

This works fine.

<?php
  //date in mm/dd/yyyy format; or it can be in other formats as well
  $birthDate = "12/17/1983";
  //explode the date to get month, day and year
  $birthDate = explode("/", $birthDate);
  //get age from date or birthdate
  $age = (date("md", date("U", mktime(0, 0, 0, $birthDate[0], $birthDate[1], $birthDate[2]))) > date("md")
    ? ((date("Y") - $birthDate[2]) - 1)
    : (date("Y") - $birthDate[2]));
  echo "Age is:" . $age;
?>